Recipe for a Saturn‐Like Dynamo

Abstract

Abstract The Cassini Grand Finale orbits provided detailed observations of Saturn’s internal magnetic field. Unique characteristics of the observed field, such as its axisymmetry and power spectrum, provide constraints on dynamo processes deep in Saturn’s interior. Here, we use numerical dynamo simulations to explore what ingredients are necessary in a dynamo in order to produce the unique “Saturn‐like” surface magnetic field. We find that characteristics of Saturn’s magnetic field can be sensitive to properties of a stably stratified helium rain‐out layer and thermal perturbations at the top of the layer. Our best models suggest that a relatively thick stably stratified helium rain‐out layer may extend out to 70% of Saturn’s radius, likely imprinted with weak heat flux out of the equatorial region and strong heat flux out of high latitudes. These results may provide new constraints on stable stratification inside Saturn and its thermal evolution.

Keywords

• dynamos
• helium immiscibility layer
• numerical simulations
• planetary magnetic field
• Saturn’s interior